1. Field of the Invention
The present invention relates to a lens unit for use in camera and a camera preferably applied for a video camera, and more particularly to a lens unit preferably used for taking stereoscopic pictures and camera thereof.
2. Description of the Related Art
Recently, various camera structures have been proposed as the stereoscopic television camera.
In this stereoscopic cameras, there are two-camera type in which a picture for the right eye and a picture for the left eye are taken with two cameras and a single lens type in which pictures for the right eye and left eye are taken with a single camera.
In case of the two-camera type, a stereoscopic image is created by generating a parallax between pictures from the two cameras.
On the other hand, in case of the single lens stereoscopic system, a phenomenon that a parallax is generated in a large lens also is utilized.
Thus, in the single lens stereoscopic system, as shown in FIG. 16, an optical shutter 53 for shielding the divided right and left portions are provided in front of a lens 52 of the camera 51. An optical path is divided to two sections by the optical shutter 53 and pictures are taken by switching over right and left optical paths by every vertical or horizontal operation.
In FIG. 16, only the right optical path is indicated in the right half. Then, the left optical path is indicated in the left half with solid line while the right optical is indicated with dot line in order to compare.
With this structure, an image for the right eye for a stereoscopic picture is taken by opening a right eye shutter 53R and an image for the left eye is taken by opening a left eye shutter 53L.
In FIG. 16, a focal point is placed on an object 55 in an intermediate distance (for example, man) so that the object 55 is in focus on an image pickup plane 57.
At this time, an object (for example, mountain) 54 farther from the focal point 55 is in focus in front of the image pickup plane 57 so that a blurred image is formed on the image pickup plane 57 and represented on an opposite side to the shutter through which the corresponding light passes, that is, the left eye image is formed to the right relative to the center while the right eye image is formed to the left relative to the center.
An object (for example, flower) 56 nearer the focal point is in focus behind the image pickup plane 57 so that a blurred image is formed on the image pickup plane 57. Then, that object is represented on the same side as the shutter through which the corresponding light passes, that is, the left eye image is formed to the left relative to the center while the right eye image is formed to the right relative to the center.
Consequently, the left eye image 58L and the right eye image 58R formed on the image pickup plane 57 are represented at deviated positions to the right and left corresponding to a distance to the object even if it is located just in front.
By using this phenomenon as parallax information and then watching two images in combination therewith, a stereoscopic image can be produced depending on a distance up to the object.
However, the above described stereoscopic television camera based on the single-lens stereoscopic system cannot be applied to a system having zooming function by a zoom lens sufficiently.
If the above described shutter for switching the right and left images is disposed in front of lenses including the zoom lens, although there is no problem on the telescopic side of the zoom, vignetting or shading, in which the right or left edge is chipped (becomes invisible) may be sometimes generated on each of the right and left screens L, R as shown in a diagonal line of FIG. 17.
If such a vignetting is generated, use of the zoom lens is limited, for example, the zoom range has to be narrowed.
Thus, it is difficult to apply the zoom function to the stereoscopic camera.